This invention relates to pig injectors used to inject pigs into pipes, and also to methods of operating pig injectors.
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Pig injectors having magazines for storing several pigs have been known at least since issuance of Canadian patent no. 649,678 and U.S. Pat. No. 3,028,996 by the inventor of the present invention. In these patents there is described a pig injector for injecting spherical pigs into a pipe, in which the pigs fall from a magazine into a T section extending perpendicularly from the pipe. The pigs may then be injected by a piston and rod arrangement into the pipe.
There is also known a multiple pig launching system made by ITAG. In this design, plural spherical pigs are stored in a magazine and released, one at a time, by a solenoid controlled finger into a rotatable pig launching valve. The pig launching valve has a ball with an interior bore and stops at the end of the bore for preventing the pig from moving the wrong way once the pig is placed in the pipe.
A further design for the launching of spherical pigs into a pipe is shown in U.S. Pat. No. 4,435,872 of Leikam. This design allows for the introduction of pigs without impeding flow of fluid in the pipe.
None of these designs is suitable for the introduction of elongate pigs into a pipe, and they require somewhat complicated metering systems, so that only one pig at a time is injected into the pipe. The present invention provides in accordance with one aspect of the invention a pig injector for injecting multiple elongate pigs and in accordance with another aspect a simplified metering design. An indicator of pig level in the magazine is also provided.
There is therefore provided in accordance with one aspect of the invention, a pig injector, comprising a magazine having a plug at one end and connected to a pig injector valve at the other end. The pig injector valve has a rotatable pig receiving chamber with a length L. Plural pigs of length L between ends, at least one of which ends and preferably both of which ends are rounded, are positioned end to end within the elongate interior cavity of the magazine.
In accordance with a further aspect of the invention, the pigs are spherical and the length of the pigs is their diameter. The rotatable pig receiving chamber may be defined by a blocked bore formed within a ball in the pig injector valve.
In accordance with a further aspect of the invention, the pigs are elongate. The rotatable pig receiving chamber may be a bore formed within a ball in the pig injector valve, with the diameter of the ball substantially equal to L.
In a further aspect of the invention, means, for example a weight, are provided to force pigs along the magazine towards the pig injector valve.
In a further aspect of the invention, a pig injector with an elongate magazine is provided with a pig level indicator indicative of the number of pigs in the magazine.
In a further aspect of the invention, the pig level indicator comprises a magnetic element within the magazine that moves with the pigs and visible magnetic sensors on the outside of the magazine. The magnetic element may be a magnet and the visible magnetic sensors may be hinged and spaced along the magazine such that location of the magnet adjacent a visible magnetic sensor causes the visible magnetic sensor to be displaced.
In a further aspect of the invention, the pig injector may include an indentation in the plug for receiving a C-wrench.
In a further aspect of the invention, there is provided a method of injecting pigs into a pipe at a pig injector valve, in which the pig injector valve has an interior rotatable ball with a bore formed within the ball, the bore and ball forming a rotatable pig receiving chamber having a length L. The method may be comprised of:
(a) storing plural pigs in a magazine connected to the pig injector valve;
(b) rotating the ball of the pig injector valve to be in position to receive a pig and close the pipe;
(c) moving a pig from the magazine into the pig injector valve;
(d) rotating the ball of the pig injector valve to open the pig injector valve and release the pig in the pipe;
(e) moving the pig away from the pig injector valve with fluid pressure in the pipe; and
subsequently repeating steps (b)-(e) with a second pig. Steps (b)-(e) may be repeated plural times and at regular intervals.
In a further aspect of the invention, a method of securing pigs within a magazine comprises:
providing a magazine with an elongate interior cavity and an open end;
inserting plural pigs into the elongate interior cavity through the open end;
threading a plug onto the open end of the magazine; and
tightening the plug with a C-wrench.
These and other aspects of the invention are described in the detailed description and claims that follow.